I just thought of an idea that has probably been mentioned before, but what do you think about adding model trains and track? Would it be possible to have something like you buy track, (including different types of track like curves, straights, splits, rises, etc.), and you buy a train and it automatically follows those tracks. The train should have a controller that would be placed in the item bar that can control speed and things like the whistle. If possible, different types of trains and cars that can be attached.
Let me know what you think.